1. Introduction
This manual provides essential instructions for the safe installation, operation, and maintenance of your Mr. Heater Heatstar MH25NG Natural Gas Radiant Overhead Garage Heater. Please read this manual thoroughly before attempting to install or operate the heater. Retain this manual for future reference.
The MH25NG is designed to provide radiant heat for spaces up to 500-600 square feet, typically found in 2-1/2 car garages or similar low-profile buildings with 7-8 ft. ceilings. It operates on natural gas and does not require electricity for heating, making it functional during power outages.
2. Safety Information
WARNING: Improper installation, adjustment, alteration, service, or maintenance can cause property damage, injury, or death. Read the installation, operating, and maintenance instructions thoroughly before installing or servicing this equipment.
- This heater is for use with natural gas only. Do not attempt to use with propane or any other fuel.
- Proper ventilation is critical. Ensure adequate fresh air supply to prevent carbon monoxide accumulation. Consider installing a carbon monoxide detector in the heated space.
- Do not use this heater in sleeping quarters, mobile homes, or recreational vehicles.
- For elevations above 2000 ft., the heater's BTU output should be reduced at a rate of 4% for each 1000 ft. above sea level, or as specified by local authorities.
- Installation and service must be performed by a qualified installer, service agency, or gas supplier.
- Maintain proper clearances from combustible materials as specified in the installation instructions.
3. Setup and Installation
3.1 Package Contents
Verify that all components are present before beginning installation:
- Radiant Heater Unit (Model MH25NG)
- Mounting Brackets
- Thermostat
- Wall Vent (for optional ventilation)
- Fasteners (screws)
Image: The complete package contents, showing the main heater unit, two black mounting brackets, a white thermostat with wire, and a white louvered wall vent.
3.2 Mounting the Heater
Mount the heater securely to a wall or ceiling structure using the provided mounting brackets. Ensure the mounting location allows for proper clearances from combustible surfaces and provides adequate space for gas line connection and maintenance.
Image: The radiant heater unit shown mounted on a wall at an angle, illustrating the typical installation position.
3.3 Gas Connection
Connect the natural gas supply line to the heater's gas inlet. This connection must be made by a qualified professional in accordance with all local codes and regulations. Ensure all connections are leak-tested before operation.
Image: A detailed view of the gas control valve, indicating the pilot adjustment screw and the main control knob with 'OFF', 'PILOT', and 'ON' positions.
3.4 Thermostat Wiring
Connect the included millivolt thermostat to the heater using appropriate thermostat wire (not included). Position the thermostat in a location that accurately reflects the ambient temperature of the heated space, away from direct heat sources or drafts. The provided thermostat wire is approximately 10 feet long; a longer wire may be needed for optimal placement.
3.5 Ventilation
Install the provided wall vent or ensure another method of adequate ventilation is in place. Proper ventilation is essential to prevent the buildup of combustion byproducts, including carbon monoxide.
4. Operating Instructions
4.1 Initial Startup and Pilot Ignition
- Ensure the gas supply valve to the heater is open.
- Turn the thermostat to its lowest setting.
- Locate the gas control knob on the heater (refer to image in Section 3.3). Push the knob in and turn it to the 'PILOT' position.
- While holding the knob in, light the pilot burner with a match or lighter. Continue to hold the knob in for approximately 30-60 seconds after the pilot flame is established, then release. The pilot flame should remain lit. If it extinguishes, repeat the process.
- Once the pilot is stable, push the knob in and turn it to the 'ON' position.
4.2 Heater Operation
Set the thermostat to your desired temperature. The heater will automatically cycle on and off to maintain the set temperature. The radiant heat directly warms objects and people in the space, which in turn warms the surrounding air.
This heater operates without electricity, providing heat even during power outages. It is designed for quiet, clean, and odor-free operation.
5. Maintenance
The Mr. Heater Heatstar MH25NG is constructed with non-corrosive materials and has no moving parts, which minimizes maintenance requirements. However, regular inspection and cleaning are recommended to ensure optimal performance and safety.
- Annual Inspection: It is recommended to have the heater inspected annually by a qualified service technician to ensure all components are functioning correctly and safely.
- Cleaning: Keep the heater's radiant surface and air inlets free from dust and debris. Use a soft brush or vacuum cleaner to gently remove any accumulation. Do not use abrasive cleaners or solvents.
- Pilot Light: Periodically check the pilot flame for proper size and color (a strong blue flame). If the pilot flame appears weak or yellow, contact a qualified service technician.
6. Troubleshooting
If your heater is not operating correctly, review the following common issues before contacting a service professional:
- Heater does not ignite:
- Check if the gas supply valve is fully open.
- Ensure the pilot light is lit. If not, follow the pilot ignition steps in Section 4.1.
- Verify the thermostat is set above the current room temperature.
- Pilot light will not stay lit:
- Ensure you are holding the gas control knob in for the recommended 30-60 seconds after lighting the pilot.
- Check for drafts that might be extinguishing the pilot.
- A faulty thermocouple may be the cause; contact a qualified technician for replacement.
- Insufficient heat:
- Confirm the heater's BTU output is appropriate for the space size and insulation.
- Ensure the thermostat is functioning correctly and placed optimally.
- Check for obstructions around the heater or excessive ventilation.
- Odor or unusual sounds: Immediately turn off the gas supply to the heater and contact a qualified service technician. Do not attempt to operate the heater if you detect gas odors or unusual noises.
IMPORTANT: If you suspect a carbon monoxide issue (e.g., headaches, dizziness, nausea), immediately evacuate the area and seek fresh air. Contact emergency services and a qualified gas technician. Ensure proper ventilation and consider installing a carbon monoxide detector.
7. Specifications
| Model Number | MH25NG |
| BTU per hour | 25,000 |
| Fuel Type | Natural Gas |
| Heating Area | Up to 500-600 sq. ft. |
| Recommended Ceiling Height | 7-8 ft. |
| Dimensions (L x W x H) | 29.75 x 12 x 9 inches |
| Material | Alloy Steel |
| UPC | 089301254442 |
8. Warranty Information
For detailed warranty information, please refer to the official documentation provided with your Mr. Heater Heatstar MH25NG heater or visit the Mr. Heater official website. Keep your purchase receipt as proof of purchase for any warranty claims.
9. Support
If you have questions regarding the installation, operation, or maintenance of your Mr. Heater Heatstar MH25NG heater that are not covered in this manual, please contact Mr. Heater customer support or a qualified service professional. Do not attempt to repair the unit yourself.
